In the field of data processing equipment magnetic recording discs have long been used for providing readily accessible external data storage. Such discs have conventionally been used with suitable drive and recording apparatus and are frequently made readily removable from such apparatus. To provide for accurate, high-density recording of data on such recording discs, it has generally been found necessary to provide recording and reading heads extending inwardly of the periphery of the disc and spaced a very few thousandths of an inch above the surface of the disc. Because of this close head-to-disc spacing it is necessary that the surface of the disc be maintained essentially free of external contaminants such as dust and dirt. The presence of even tiny dust or dirt particles on the surface of the disc could result in interference between the dust particles and the disc and the recording head, thus resulting in what is commonly known as "head crash." Such an undesirable condition could result either in damage to the recording head or in distortion of the data recorded or read.
To maintain the surfaces of these magnetic recording discs substantially free from such contaminants when the discs are removed from the drive apparatus, as when they are stored, it has been conventional to enclose the discs in cartridges which substantially exclude such contaminants when the disc is removed from its drive. With certain types of cartridges a small access door is openable to permit access by the recording and playback heads to the disc surface. In other units such as that commonly known as a Memorex type 5440 disc cartridge the disc is contained within an upper housing which stays with the disc at all times. With this 5440 type cartridge the upper housing and the disc contained therewithin may be received within a separably mating lower housing which, with the upper housing, forms a substantially dust-tight enclosure. With this arrangement the upper housing and disc are mated with the lower housing as soon as the disc and upper housing are removed from the drive, thus protecting the disc surfaces.
In the 5440 type cartridge the lower housing is held securely to the disc and upper housing by engagement by magnets mounted to the lower housing with the steel hub of the disc contained in the upper housing. Separation of the upper and lower housings is effected by axial movement of the disc and its hub away from contact with those magnets. This axial movement has conventionally been provided by a lifting arrangement associated with a carrying handle pivotally connected to the upper housing, acting through a complex assembly in which a latch is slidably mounted to the handle and can be moved into position to engage an eccentrically operating structure for lifting the disc and its hub axially away from the lower housing. This arrangement, while functionally satisfactory, has comprised a rather complex assembly in which the component parts are expensive to manufacture and the entire structure is expensive and time consuming to assemble.